Electric current
- Calculate the average electric current in a wire
when a charge of 150 C passes in 30s? I = Q/t
= 150/30 = 5A
- The current in a small torch bulb is 0.20 A. What total electric
charge which passes through a point circuit in 12 minutes? 1.4 x102How many electrons pass
through this point in this time? 1.4 x102
/1.8 x 10-19 = 9 x 1020
- In the circuit opposite the three bulbs are identical and reach
hill brightness when the current is 0.20A. Bulb B is observed to be at
full brightness. Which (if any) of the other bulbs will be at full
brightness, and what is the current in each of them? B,C
B =
0.2A, C = 0.2A, D = 0.05A
- A new electric cell was joined in series with a bulb and an
ammeter. The initial current was 0.30 A. At subsequent intervals of
1 hour the readings on the ammeter were: 0.27A, 0.27A, 0.26A, 0.25 A,
0.23A, 0. 19A, 0.09A, 0.03 A, and at 9 hours the ammeter reading had
become negligibly small.
(a) Plot a graph of current against time.
(b) What does the area under the graph represent? Total charge
(c) How much electric charge passes through the circuit when a current of 0.10 A passes for 1 hour? 360C
(d) What is the total electric charge which passes through the cell in the 9 hours? 6.3kC - In a gas discharge tube containing hydrogen the current is carried
partly by (positive) hydrogen ions and partly by electrons. An ammeter in
series with the tube indicates a current of 1.5 mA. If the rate of passage
of electrons past a particular point in the tube is 6.0 x 1015
s-1, find the number of hydrogen ions passing the same point
per second. 3.4 x1015 s-1
